A National-level Study on Plant Phenology across Forest Region of South Korea during the last decade

Phenology is widely used as an indicator of climate change because it is sensitive to meteorological factors such as temperature and precipitation. Previous phenology studies have shown that leaf unfolding is accelerating around the world though the magnitude depends on the area. However, phenology research of South Korea was mostly focused on the leaf unfolding only in the urban areas. In this study the changes of leaf unfolding and leaf fall in temperate forest of South Korea and the relationship with temperature, using data of the forest area collected from 50 observation sites in 10 South Korea National Arboretums.

Result showed that leaf unfolding was accelerating 1.37 day per year, and the timing of leaf fall was delaying 0.34 day per year during the last decade. In terms of species, the most sensitive species was Lindera obtusiloba which had 1.82 earlier days by year. The leaf unfolding of Magnolia denudate were the least sensitive among the 7 species which had 1.07 earlier days by year. To understand the reason of changes of the leaf unfolding and leaf falls, temperature data was compared to the regional meteorological data observed by the Korea Meteorological Administration (KMA). Both leaf unfolding and leaf fall showed the highest correlation with the mean temperature of the preceding season. The timing of the leaf unfolding becomes 4.20 days per year with the increased 1℃ in average spring temperature. The timing of the leaf falls becomes 2.78 days delayed per increased 1℃ in the mean temperature in October. However, some early leave fall was occurred in 2014, 2016 when the extreme heat wave recorded. This means that extreme weather such as heat wave and drought should be considered with temperature to understand the leaf fall.